Messages in this thread Patch in this message |  | | From | Roger Larsson <> | Subject | Re: ksoftirqd? (Was: Re: [PATCH] Preemption Latency Measurement Tool) | Date | Sat, 22 Sep 2001 22:51:16 +0200 |
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On Saturday 22 September 2001 15.14, Andrea Arcangeli wrote: > On Sat, Sep 22, 2001 at 02:56:58PM +0200, Roger Larsson wrote: > > Hi, > > > > We have a new kid on the block since we started thinking of a preemptive > > kernel. > > > > ksoftirqd... > > > > Running with nice 19 (shouldn't it really be -19?)
I repeat this question - should it be nice 19 and not nice -19 (not nice)?
> > Or have a RT setting? (maybe not since one of the reasons for > > softirqd would be lost - would be scheduled in immediately) > > Can't a high prio or RT process be starved due to missing > > service (bh) after an interrupt? > > It cannot be starved, if ksoftirqd is never scheduled the do_softirq() > will be run by the next timer irq or apic_timer irq. >
Then could you please explain the output after adding a printk in ksoftirqd like this.
--- kernel/softirq.c~ Mon Sep 17 22:37:34 2001 +++ kernel/softirq.c Sat Sep 22 21:46:49 2001 @@ -387,6 +387,7 @@ __set_current_state(TASK_RUNNING);
while (softirq_pending(cpu)) { + printk("ksoftirqd: do_softirq\n"); do_softirq(); if (current->need_resched) schedule();
Output like this:
Sep 22 22:37:38 jeloin logger: *** ./stress_dbench begin *** Sep 22 22:37:42 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:37:44 jeloin last message repeated 2 times Sep 22 22:37:48 jeloin kernel: Latency 8ms PID 7 %% kupdated Sep 22 22:37:49 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:38:19 jeloin last message repeated 18 times Sep 22 22:38:20 jeloin su: (to root) roger on /dev/pts/2 Sep 22 22:38:20 jeloin PAM-unix2[988]: session started for user root, service su Sep 22 22:38:23 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:38:24 jeloin modprobe: modprobe: Can't locate module net-pf-10 Sep 22 22:38:24 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:38:58 jeloin last message repeated 20 times Sep 22 22:39:05 jeloin last message repeated 4 times Sep 22 22:42:03 jeloin kernel: ksoftirqd: do_softirq Sep 22 22:43:58 jeloin logger: *** ./stress_dbench end ***
> > This will not show up in latency profiling patches since > > the kernel does what is requested... > > > > Previously it was run directly after interrupt, > > before returning to the interrupted process... > > It is still the case, that's also the common case actually. >
Possibly but the other case is quite common too...
/RogerL
-- Roger Larsson Skellefteå Sweden - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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